DENVER – In a showdown at close quarters, President Barack Obama and Republican Mitt Romney sparred aggressively in their first campaign debate Wednesday night over taxes, deficits and strong steps needed to create jobs in a sputtering national economy. "The status quo is not going to cut it," declared the challenger.

Obama in turn accused his rival of seeking to "double down" on economic policies that actually led to the devastating national downturn four years ago.

Both men made frequent references to the weak economy and high national unemployment, by far the dominant issue in the race for the White House. Public opinion polls show Obama with a slight advantage in key battleground states and nationally, and Romney was particularly aggressive, like a man looking to shake up the campaign with a little less than five weeks to run.

Polite but pointed, the two men agreed about little if anything.

Obama said his opponent's plan to reduce all tax rates by 20 percent would cost $5 trillion and benefit the wealthy at the expense of middle income taxpayers.

Shot back Romney: "Virtually everything he just said about my tax plan is inaccurate."

The former Massachusetts governor and businessman added that Obama's proposal to allow the expiration of tax cuts on upper-level income would mean tax increases on small businesses that create jobs by the hundreds of thousands.

The two campaign rivals clasped hands and smiled as they strode onto the debate stage at the University of Denver, then waved to the audience before taking their places behind identical lecterns.

There was a quick moment of laughter, when Obama referred to first lady Michelle Obama as "sweetie" and noted it was their 20th anniversary.

Romney added best wishes, and said to the first couple, "I'm sure this is the most romantic place you could imagine, here with me."

Both candidates' wives were in the audience.

The two men debated before a television audience likely to be counted in the tens of millions. They will meet twice more this month, and their running mates once, but in past election years, viewership has sometimes fallen off after the first encounter.

Without saying so, the two rivals quickly got to the crux of their race – Romney's eagerness to turn the contest into a referendum on the past four years while the incumbent desires for voters to choose between his plan for the next four years and the one his rival backs.

Romney ticked off the dreary economic facts of life – a sharp spike in food stamps, economic growth "lower this year than last" and "23 million people out of work or stropped looking for work."

But Obama criticized Romney's prescriptions and his refusal to raise taxes and said, "if you take such an unbalanced approach then that means you are going to be gutting our investment in schools and education ... health care for seniors in nursing homes (and) for kids with disabilities."

Not surprisingly, the two men disagreed over Medicare, a flash point since Romney placed Wisconsin Rep. Paul Ryan on his ticket.

The president repeatedly described Romney's plan as a "voucher program" that would raise out-of-pocket costs on seniors.

He continued, directly addressing the voters at home: "If you're 54 or 55 you might want to listen because this will affect you."

Romney said he doesn't support any changes for current retirees or those close to retirement.

"If you're 60 or 60 and older you don't need to listen further," he said, but he contended that fundamental changes are needed to prevent the system from becoming insolvent as millions of baby boom generation Americans become eligible.

Romney also made a detailed case for repealing Obamacare, the name attached to the health care plan that Obama pushed through Congress in 2010. "It has killed jobs," he said, and argued that the best approach is to "do what we did in my state."

Though he didn't say so, when he was governor Massachusetts passed legislation that required residents to purchase coverage – the so-called individual mandate that conservatives and he oppose on a national level.

Romney also said that Obamacare would cut $716 billion from Medicare over the next decade.

The president said the changes were part of a plan to lengthen the program's life, and he added that AARP, the seniors lobby, supports it.

Jim Lehrer of PBS drew moderator's duties, with Obama getting the first question and Romney the last word.

Five weeks before Election Day, early voting is under way in scattered states and beginning in more every day. Opinion polls show Obama with an advantage nationally and in most if not all of the battleground states where the race is most likely to be decided.

That put particular pressure on Romney to come up with a showing strong enough to alter the course of the campaign.

The sputtering economy served as the debate backdrop, as it has for virtually everything else in the 2012 campaign for the White House. Obama took office in the shadow of an economic crisis but promised a turnaround that hasn't materialized. Economic growth has been sluggish throughout his term, with unemployment above 8 percent since before he took office.

The customary security blended with a festival-like atmosphere in the surrounding area on a warm and sunny day. The Lumineers performed for free, and Black Eyed Peas frontman will.i.am delivered a pep talk of sorts to Obama's supporters. School officials arranged to show the debate on monitors outside the hall for those without tickets.

There was local political theater, too, including female Romney supporters wearing short shorts and holding signs that said, "What War On Women?" — a rebuttal to claims by Obama and the Democrats.

Both campaigns engaged in a vigorous pre-debate competition to set expectations, each side suggesting the other had built-in advantages.

Romney took part in 19 debates during the campaign for the Republican primary early in the year. The president has not been onstage with a political opponent since his last face-to-face encounter with Arizona Sen. John McCain, his Republican rival in 2008.

Obama and Romney prepared for the evening with lengthy practice sessions. Romney selected Ohio Sen. Rob Portman as a stand-in for the president; Obama turned to Massachusetts Sen. John Kerry to play the Republican role.

The two presidential rivals also are scheduled to debate on Oct. 16 in Hempstead, N.Y., and Oct. 22 in Boca Raton, Fla.

Vice President Joe Biden and Republican Rep. Paul Ryan of Wisconsin have one debate, Oct. 11 in Danville, Ky. Both men have already begun holding practice sessions.